Electric hotplates are known from German Utility Model 81 03 701 containing a hotplate body made from cast material and a heating means for the same, the heating means having electrical resistors embedded in grooves on the bottom of the hotplate body, the body having an elongated flat upper surface. In plan view, such hotplates have an oval shape and on their bottom surface have a common heating system with incorporated electrical heating resistors. They are used for heating elongated cooking, baking or roasting vessels.
Circular hotplates are also known, which comprise separate or connected, heated rings. Swiss Pat. No. 187 383 shows the connection of said rings by a sheet metal strip with an expansion seam or bead.